Pollen morphology of Coffea and Psilanthus (Rubiaceae‐Coffeeae), mainly from Africa

Abstract

Twenty‐six Coffea and six Psilanthus species are examined to provide a survey of the pollen morphological variation of the African Coffeeae. These observations are compared with data from literature and evaluated by numerical analysis. The latter corroborates that the two genera are distinguishable on the basis of pollen morphology. Coffea grains are generally 3‐colporate, while Psilanthus mostly has 4–5‐colporate grains. In Coffea many species show a surprisingly high degree of pollen polymorphism. There is no doubt that this phenomenon is at least in part responsible for the poor taxonomic value of pollen features at the specific level, in this genus. As regards Psilanthus our results seem to indicate pollen morphological differences between African (more narrow muri; no supratectal ornamentation) and Asian species (muri wider; supratectal granules), but this should be confirmed by investigating more species. This is in contradiction to the actual division in subg. Psilanthus and subg. Afrocoffea.